The present invention relates to caging systems for laboratory animal care and more particularly to a cage and system which has controlled ventilation, waste containment and does not require bedding.
Most all existing ventilated rodent cage systems are made with plastic solid-bottom cages. Clear cages are used so it is possible to inspect the condition of the inside of the cage without disturbing the animals. The cage ensemble generally consists of a metal wire bar lid containing a feed hopper and water bottle capabilities and a plastic top that holds a piece of filter media. The wire bar lid is convenient to use because feed and water bottles in a cage can be moved to a clean cage in one motion. The cages are contained in a rack that holds a plurality of cages either single or double sided. An automatic water system introduces water into the cage for the rodent using lixits or water valves located either outside or inside the cage. It must be monitored for proper water pressure and must be flushed periodically. Problems of leakage, high intracage humidity levels and cage flooding are associated with automatic watering systems. A plenum, either a separate duct system or made up of components of the rack (i.e. the shelves or the tubing uprights), supply the cage with filtered air through a cage mounted air supply diffuser. The front of the cage, perimeter of the cage lid and the cage body (where the leakage occurs) is open to the environment of the animal room. The air flow is either transversely across the cage or from an inlet in the side or top of the cage to an outlet in the junction of the top and body or top of the cage. A removable bottom portion for animal waste has been disclosed but air flow through the waste tray has not been reported.
Exhausted air is drawn either through a plenum system or into a "U" shaped metal exhaust collar surrounding three sides of each cage or a metal or plastic canopy. It is drawn into a horizontal exhaust manifold on each shelf, travels up the vertical exhaust plenum, then finally into a filtered exhaust system. This system, designed for limited capture of exhausted cage air, allows contaminated air to escape into the room from the cage lid perimeter and may present health problems for personnel. The systems scavenge room air and introduce air into the room, thus disturbing the macroenvironment. Present systems allow the pressurized air to blow any contaminants on the filter media into the room. Another type allows contaminants on the filter media to blow into the cage.
The applicant is aware of the following U.S. patents which are related to cages for laboratory animals:
______________________________________ Inventor(s) U.S. Pat. No. ______________________________________ Fricke 2,467,525 Fuller et al 3,063,413 Barney 3,397,676 Holinan 3,924,571 Gland et al 4,085,705 Gass 4,154,196 Nace 4,201,153 Thomas 4,402,280 Picard et al 4,435,194 Sedlacek 4,480,587 LoMaglio 4,526,133 Spengler 4,528,941 Peters et al 4,798,171 Niki 4,844,018 Spina 4,869,206 Niki et al 4,940,017 Sheaffer 4,989,545 Niki et al 5,003,022 Niki et al 5,048,453 Coiro, Sr. et al 5,148,766 Coiro, Sr. et al 5,307,757 Sheaffer et al 5,311,836 Harr Re 32,113 Semenuk D 351,259 Semenuk D 383,253 ______________________________________
Current ventilated caging systems, of which the applicant is aware, for laboratory animal care and use in biomedical research/testing is suboptimal because of the lack of environmental control. Also, animal activity over contact bedding material, husbandry techniques and laboratory procedures generate aerosols and allergens that spread through cage leakage into the work area and pose a risk of contamination to the animals and to the workers. In addition to suspension of particulates, chilling and dehydration of neonates, hairless and nude strains, existing ventilated racks have provoked animal losses due to hypothermia. While the systems currently in use may provide some biological exclusion and save labor, the use of bedding material, the lack of animal comfort, the leakage problem, and the high cost of maintenance pose serious problems in research.
In present systems, bedding and nesting materials are placed directly on the floor of the solid-bottom cages, since rodents are nesting and burrowing animals. The primary requirements of bedding materials are: (1) the material must not be harmful to the animal; (2) it must be capable of absorbing moisture without causing dehydration of newborn animals, (3) it must not create excessive dust, (4) it must be economical to use and dispose of. So far, existing bedding materials fail to achieve these standards. A major goal is eliminating the cost of bedding and bedding-related activities including bedding ordering, receiving, storage, dispensing, autoclaving, dust removal, bedding dumping, cage-scraping, bagging, disposal and finally removal of soiled bedding. Dispensing of used bedding can engender both problems of storage and aerosol contamination including allergen exposure. Expensive engineering and operation systems are required to prevent these problems. Modern bedding disposal systems are basically vacuums, which prevent contaminated particles from getting into the air that workers breathe. The location of such systems throughout a facility and the transportation of waste bedding are major operational expenses. Moreover as greater demands are put on available space, clean bedding storage add a burden to husbandry-related costs. Thus, there is a need for a laboratory animal cage and a system of cages which solve these problems.